Optical display glass is formed in large sheets on a glass manufacturing line. The display glass needs to be inspected for defects or manufacturing anomalies prior to being further processed and included in any one of a variety of display devices. The inspection is typically optically based and usually performed in two steps: a coarse optical inspection that covers the entire glass sheet to identify locations that need to be revisited for closer inspection; and a revisit optical inspection that takes a closer look at the locations identified in the course inspection.
The revisit inspection is performed using an optical inspection system called a micro revisit station or MRS. The MRS acquires multiple images of the problematic location on the glass sheet. The multiple images are taken under different illumination conditions and at different locations at the surfaces and within the glass sheet so that the potential defect or anomaly can be more easily detected, located and characterized.
A main consideration in the optical inspection process performed by the MRS is speed. Delays in the optical inspection process result in manufacturing process delays. Such delays also prevent timely manufacturing information from being fed back into the upstream manufacturing process to allow for adjusting the manufacturing process to avoid the formation of the identified defects.